The present invention relates generally to a retrofocus type objective lens system, and more particularly to a retrofocus type objective lens system for use in a single lens reflex camera having a backfocus longer than 0.9 times the focal length of the entire lens system.
A known retrofocus type lens for use in a single reflex camera incorporates a divergent lens ahead of the entire lens system and a convergent lens in the rear half portion thereof overcoming the divergency of the aforesaid lens system, for the purpose of obtaining a long backfocus. An attempt to achieve better compensation for the aberration of the entire lens system results in a complicated construction of the lenses. The objective lenses of the retrofocus type of this kind consists of five lenses and are known as the simplest construction of lenses, i.e., consisting from the object side, a first negative lens, a second positive lens, a third negative lens, a fourth positive lens and a fifth positive lens.
According to the present invention, there is provided a small size and light weight objective lens system having an image forming capability at least equal to or better than that of the conventional retrofocus type lens system which consists of six or seven lenses, by providing an improved lens arrangement and dimensional relationship of the retrofocus type lens system consisting of five components defining five lenses.